Early instances of 'white woman'
The earliest instances of "white [or whyte] woman" in English go back very far indeed. In a search of Early English Books Online, the earliest publication date reported in search results was "1490?"—for this instance from "The spyces of exercyse," in In this tretyse that is cleped Gouernayle of helthe what is to be sayd wyth crystis helpe of some thynges that longen to bodily helthe, which focuses on the relative merits of a "broun woman" and a "white woman" in winter and in summer:
Yet ther ben other maners of exercyse for yonge men that ben lusty as to renne to wrastle to lepe to caste the stone / and so of other playes also tempred fleshly companyng wyth a yōg broun woman is goode in wynter / and wyth a yonge white woman ys goode in somer is also goode & helpyng in gouernyng of helthe to body but not to soule / excepte to hem then that mowen haue it by goddes lawes so ne∣theles that thee be so moche tym bytwene that he fele hym selse eased & lyghtened in his body and that he ete the better & slepe the better
Differing heat in white and brown women is also argued in a 1537(?) translation of a French text, The history of kyng Boccus:
After which aman loke shal / What woman he shal dele with al / In wynter whan the ayre is colde / And his keelth yeldes manyfolde / A yong woman and broune also / Profytes than man vnto / For broune woman is of hote onde / And of hote guttes fonde / And her hete hetys man also / And great profyt doys hym to / In somer whan the ayre is hote / And heteth both drye and wote / Than is a yong whyte woman / Best vnto profyt of man / For she is colde of kynde to fele / And man of great hete may she kele ...
It is not clear, however, whether brown and white here mean "dark-skinned" and "light-skinned" or "relatively dark" and "relatively light" or "brunette" and "blonde."
Thomas Hill, The contemplation of mankinde contayning a singuler discourse after the art of phisiognomie (1571) echoes the two sources cited in JEL's original question—but here the discussion is preceded by a comment about redheads:
The redde colour of the heares of the head in∣tensed, is a note of craftie wiles and deceytes, of much yre, and of fransinesse, when as the same declareth the aboundance of choller.
Then comes this paragraph:
The browne Chestnut colour, doth declare vprightnesse, and the loue of iustice: and all report, especially Nuncius naturae, in the seuenth booke of the nature of beastes, and in the first Chapi∣ter, of the condition of a Nurse, where he vttereth, that of those, the better and healthfuller sort are they, which be browne in colour, than the whyte woman, and haue a helthfuller milke: the selfe same affirmeth Auicen. 4. de animalibus
So is the brown chestnut color a skin color or a hair color? And on what feature is the whiteness of the white woman determined?
A metaphorical discussion of "the white woman" and "the red man" appears in George Ripley, The compound of alchymy (1471(?)/1591) in the context of alchemy:
Consider first the latitude of this precious Stone, / Beginning in the first side noted in the West, / Where the red man & the white woman be made one, / Spoused with the spirite of life to liue in rest, / Earth and water equally proportionate, that is best, / And one of the earth is good, and of the spirit three, / Which twelue to fowre also of the earth may bee.
Three of the wife, and one of the man thou take, / And the lesse of the spirit in this dispousation, / The rather thy Calcination for certain shalt thou make: / Then forth into the North proceed by obscuration / Of the red man and his white wife, called Eclipsation, / Loosing them and altring them betwixt winter & vere, / Into water turning earth, darke and nothing cleare.
The discussion here is of the way to obtain the philosopher's stone through a series of chemical processes isolating and purifying the virtuous material after first combining various gross original substances. Ripley died in 1490 (approximately), and various versions of this text date the original to 1471 or 1477. The marriage of personified white and red substances thus appears in a pre-Columbian European context.
The earliest EEBO instance I could find where "white woman" appears in an unmistakably racial context is in the 1594 M. Camillo Camili translation of Iohn Huarte, Examen de ingenios [The examination of men's wits] (by 1588), where the author uses interracial offspring to call into question Aristotle's explanation of human generation:
Moreouer, if a womans seed were of that maner which Aristotle mentioneth, it could be no proper aliment: for to attain the last qualities of actual nutriment, a totall seed is necessarie, whereby it may be nourished. Wherthrough, if the same come not to be concocted & semblable, it cannot performe this point: for womans seed wanteth the instruments and places, as are the stomacke, the liuer, and the cods, where it may be concocted. Therefore nature prouided, that in the engendring of a creature, two seedes should concurre; which being mingled, the mightier should make the forming and the other serue for nourishment. And this is seen euidently so to be: for if a blackamore beget a white woman with child, & a white man a negro woman, of both these vnions, wil be borne a creature, partaking of either qualitie.
The earliest dictionary definition related to "blackamore" that I've been able to find is this one from Thomas Dyche & William Pardon, A New General English Dictionary, third edition (1740):
BLACKS or BLACK MOORS (S.) many nations of people under or near the equinoctial line, who are of a black colour, among which those who have short curled hair are called Negroes.
Here, at least, black moor refers exclusively to a person who lives in the tropics and whose skin is black. I think it is likely that the word had a similar meaning in English a century and a half earlier when Camili used it.
Early instances of 'white women'
Early English Books Online reports an instance of "whyte women" from The grete herball whiche geueth parfyt knowlege and vnderstandyng of all maner of herbes (1526), but I have not been able to find a accessible copy of this book online. A Hathi Trust search for "whyte women" doesn't confirm the existence of "whyte women" or "white women" in The grete herball.
The next instance that EEBO searches produce is to The problemes of Aristotle with other philosophers and phisitions (1595)—the second quotation cited in JEL's original question. Then comes this instance from Iohn Huighen van Linschoten, his discours of voyages into ye Easte & West Indies Deuided into foure bookes (1598):
The Prouince of Bracamoros, is about sixtie miles from Quito: trauailing along the hill about fiue and fortie miles further, lyeth the Prouince of Chichapoyas, or Cachapoas, wherein the Spaniardes haue a towne called Frontiera, on Leuanto, where the countrey is verie fruitfull of all kinde of Spices, and of rich Golde mynes: Leuanto by reason of the scituation of the place, is verie strong, and well kept, as be∣ing almost compassed about with a deepe vallie, wherein for the most part there runneth a certaine riuer, whereby the towne of Frontier builded vppon Leuanto, is not easie to bee woonne, if the bridges be once broken downe. This prouince was built with houses, and peopled with inhabitants of the Spanish nation, by Alonzo de Aluarado, in the yeare of our Lord 1536. Therin are faire and white women, fairer then in any other parte of Peru, also very gracious and courteous, and withall, verie well apparrelled.
The "white women" in this case are women of Spanish origin, living (and in some instances born) in Peru. The situation here seems especially relevant to "white women" as a descriptive term for women belonging to a particular racial or pseudo-racial category, since the women mentioned here appear in a part of the world where relatively few women of European ancestry lived in the late 1500s.